Furnace



Oct. 11, 1932. w s 1,881,732

FURNACE Filed Jan. 16, 19551 2 Sheets-Sheet 1 |NV ENTOR George R. L ewer BY ATTORNEYS G. R. LEWERS Oct. 1, 1932.

FURNACE Filed Jan. 16.

1931 2 Sheets-Sheet 2 INVENTOR 6e0rye F.18WCI'J BY 72,41 @gjkwQi-M ATTORNEY$ Patented Oct. 11, 1932 UNITED STATES PATENT OFFICE.

FURNACE Application filed January 16, 1931. Serial No. 509,101.

My invention relates to improvements in the burning or roasting of solids containing vaporizable combustible material, such as 011 saturated mineral absorbents and sulphur bearin ores. My invention is of special value an ap licationin connection with the burning 0 such mineral absorbents to recover them for reuse. It is also useful in roasting of such ores, particularly for the 1 elimination of sulphur.

Burning operations to recover oil saturated mineral absorbents such as fullers earth, clays and like materials, to recover them for reuse are commonly carried out in tiered multiple hearth furnaces provided with rotary rabbles driven from a common shaft extending vertically through the several hearths, the oil saturated absorbent belng supplied to the uppermost hearth, the oil content'of the absorbent 'being utilized as fuel for the operation and the burned product being discharged from the lowermost hearth. This common ractice frequently involves a loss of as muc as to or more of the absorbent and, unfortunately, the lost material almost invariably includes a more than aliquot portion of more active compo nents of the absorbent with the result that the recovered material is of reduced efficacy. In working on this problem I have found that this loss seems to be due to more or less uncontrolled eombustion particularly on the first few hearths over which the oil saturated absorbent passes. My invention provides for control of combustion in the burning operation in an advantageous manner accomplishing a substantial improvement with respect to such losses without involving sacrifice of furnace capacity and without prejudice, but rather the contrary, to the efiicacy of the burned product. My invention includes an improved burning operation and an improved apparatus of special value and application for carrying out such burning operations.

In carrying out my invention to recover such mineral absorbents I first pass the oil saturated mineral absorbent through a region, over the first hearth or the first several hearths of the burning furnace for example,

in which combustion is controlled by limitation of the air available for combustion and in which, by such control of combustion, vaporization of a large part of the contained oil from the absorbent is effected without combustion of this part of such oil, and then pass the absorbent, thus partially freed from its original oil content, through a separate region, over successive hearths of the burning furnace for example, in Which combustion is 60 controlled by limitation of the fuel available for combustion, the oil vaporized from the absorbent in the first mentioned region for example, or by regulated distribution through this second region, through the several hearths of which it is comprised for example, of the fuel available for combustion. I maintain reducing conditions in the first region and oxidizing conditions in the second. I thus am able to carry out the burning operation so that combustion proceeds regularly and under definite control throughout the various stages of the operation and in this manner I avoid excessive losses of the absorbent and in particular losses of more active components of the absorbent. I have been able, by my invention, to accomplish recoveries of a burned product as high as 98% of the absorbent content of the oil saturated material charged to the operation and of a burned product improved as much as 50% or more in efficacy without sacrifice of furnace capacity in burning furnaces of the same size and same general construction as are commonly used for the purpose.

My invention will be further described in connection with the accompanying drawings which illustrate in a diagrammatic and conventional manner apparatus adapted for carrying out my invention. It is intended and will be understood that this further and more detailed description of particular embodiments of my invention is intended by way of exemplification only and that my invention is not limited to the specific operations described by way of example, or to the specific apparatus illustrated. In the accompanying drawings:

Fig. 1 is a fragmentary elevation in sec- 1 tion with parts broken away of a furnace embodying my invention and adapted for carrying out my invention.

Fig. 2 is a section on line 2-2 of Fig. 1,

I and described in detail here. a

In carrying out my invention to recove such mineral absorbents in the furnace illustrated in Fig. 1, oil saturated mineral absorbent material is supplied to the uppermost hearth 11 through chute 10 by means of a conventional screw feed mechanism 9. The rotation of the rabbles carries this material across the hearth 11 to be dropped to the hearth 12 and thence across the hearth 12 to be delivered through the chutes 8 to the hearth 15. The material delivered from the chutes 8 is carried successively across the hearths 15, 16, 17, 18, 19 and 20, etc., from the last of which it is discharged through chutes 7 to conventional collection means. Air for combustion on the hearths 15, 16, 17, 18, 19 and 20, etc., also enters through the chutes 7.

In the furnace illustrated a temperature sufiicient to vaporize a large part of the oil content of the material supplied through the chute 10 is maintained by burners inserted through the apertures 6 and 5 (see Fig. 2) but the supply of air admitted is limited by suitable slides 5a and 6a to avoid combustion in excess of that required to effect this vaporization. The vaporized oil escapes throu h the ducts 4 to the conduits 21. Instead of positioning the burner apertures 5 and 6 on the hearth 12 as in the apparatus illustrated, these burner apertures 5 and 6 may be positioned on the hearth 13 and the heat necessary for the vaporization then transferred to the hearth 12 by constructing this hearth of material of relatively high thermal conductivity such as silicon carbide. Extreme limitation of air available for combustion on the hearths 11 and 12 may thus be effected.

It will be noted that the conventional openings to permit material to be dropped to the next lower hearth are not present in the hearth 12. The hearth 12 completely divides the furnace except for the chutes 8. These conventional openings 14' are present in the hearth 14. Gases escaping from the hearth 15 and the hearths below it pass through the openings 14 in the hearth 14 and the central opening through the hearth 13 to the stack flue 22 through which they escape.

The separation of oil effected by vaporization on the hearths 11 and 12 avoids irregular or uncontrolled combustion on hearth 15, or the hearths below it, to which the material from which oil has been separated by vaporization on the hearths 11 and 12 is supplied through the chutes 8. On the hearth 15, and the hearths below it, the heat necessary to complete burning of th mineral absorbent is supplied by combustion of fuel from burners inserted through apertures 6 and 5. The supply of fuel from these burners, being independent of the rate of supply of the absorbent to these hearths is readily susceptible to control. The oil vaporized from the absorbent on the hearths l1 and 12 and discharged through the ducts 4 to the conduits 21, or any required part of these oil vapors, are with advantage supplied from the conduits 21 to any one or more of the hearths 15, 16, 17, 18, 19, 20, etc., through the ducts 23 and 24 for example, as may be necessary or desirable in the particular operation. Th utilization of these oil vapors, or part of them, as fuel on the hearths on which burning of the absorbent is completed is comprehended within my invention. Any excess of these oil vapors over that required for combustion on the hearths on which burning of the absorbent is completed may be conveyed from the conduits 21 through conduit 25 to the condenser 26.

Dampers are provided as illustrated in the ducts 4, 23 and 24 and the conduits 21 and 25 for control of the flow of the oil vaporized from the absorbent on the hearths 11 and 12.

The hearth chambers including hearths 14 and 13 constitute settling and collection chambers for the separation from escaping ases of entrained fines for return to the heart 15. These hearths 14 and 13 are outside of any region of active combustion and, in conjunction with my invention, assist in elimination of loss of fines. Such fines frequently are a most eflicacious component of mineral absorbents. The provision of such settling and collection chambers is not essential to secure many of th advantages of my invention but my invention comprchends the provision of such chambers or of the operation effected in such chambers in conjunction with the rest of the apparatus and operation of my invention.

Passage of material through the chutes 8 to maintain a seal to prevent passage of gases from the hearth 15, or the hearths below it, or from the hearths 13 and 14, over the hearths 11 and 12 may be controlled in any conven tional manner. In the apparatus illustrated in Figs. 1 and 2 counterpoised closure means adapted to maintain a predetermined weight of material in the chutes 8 are shown. In the apparatus illustrated in Fig. 3 closure means adapted to be opened periodically through linkages 30 and 31 actuated by a cam 32 pcsitioned onthe rabbl shaft are shown.

It will be apparent that my invention provides for control of combustion, or rate of burning of the mineral absorbent, throughout burning operations for the recovery for reuse of mineral absorbents saturated with combustible oil. The elimination of contained oil from the absorbents is one of the functions of such recovery operations. In carrying out my invention this may be in art accomplished in the preliminary stages oFth burning operation with or without combustion of part of the contained oil. In carrying out my invention as distinguished from conventional practice, however, uncontrolled or irregular combustion of this oil in the preliminary stages of the burning operation is avoided, and further more effective control of combustion in succeeding stages of the burning operation is attained by such elimination of uncontrolled or irregular combustion in the the preliminary stages. This control of the later stages of the burning operation may be accomplished by control of the amount of heat supplied or by control of the distribution of the total heat supplied or by control in both of these respects. The thorough control of combustion throughout the burning operation thus rovided by my invention affords equally thorough control of the temperature gradient throughout the burning operation.

Roasting operations to desulphurize ores, of zinc, antimony and lead for example, also are commonly carried out in such tiered multiple hearth furnaces, the ore being su plied to the uppermost hearth and the roaste product being discharged from the lowermost hearth. In this common practice it is difficult to maintain the temperature on the uppermost hearths below the required maximum and at the same time to maintain proper roasting conditions. Excessive temperatures on these hearths usually involve loss of fines and also undesirable nodulizing or sintering, inhibiting elimination of sulphur, of the ore. The sulphur content of such ores is frequently suflieient to support combustion at high temperatures, but uncontrolled combustion of the sulphur at such temperatures produces an unsatisfactory roasted product. My inventionincludes an improved roasting operation and an improved apparatus of special value and application for carrying out such roasting operations.

In carrying out my invention to roast such ores I first pass the sulphur bearing ore through a re ion, over the first hearth or the first several earths of the roasting furnace for example, the hearths 11 and 12 of the furnace illustrated, in which reducing conditions are maintained by limitation of the air available for combustion and in which a temperature sufficient to vaporize sulphur from the ore is maintained, in the manner previousl described, and then pass the ore, thus partlally freed from its original sulphur content, through a separate region, over successive hearths of the roastin furnace for example, the hearths 15, 16, 1 etc., of the furnace illustrated, in which oxidizing corn ditions are maintained usually by the combustion of extraneous fuel. Proper roasting conditions may thus be maintained without involving danger of excessive temperatures. The va orized sulphur may be vented to the atmosphere or conveyed to a parat'us approriate for the manufacture of sulphuric acid, or example. The gases escaping from the region in which oxidizing conditions are maintained do not pass through the region in which the initial elimination of sulphur is efi'ected.

It will be apparent that my invention provides for control of combustion, or the roasting conditions, throughout roasting operations for the desulphurization of ores. Uncontrolled or irregular combustion of the sulphur content of the ore is avoided and more effective control of the roasting operation is attained. Control of the several stages of the roasting operation may be accomplished by control of the amount of extraneous fuel supplied or by control of the distribution of combustion of extraneous fuel supplied or by control in both of these respects. The thorough control of combustion throughout the roasting o ration thus provided by m invention a ords equally thorough contro of the temperature gradient throughout the roasting operation.

Having described my invention, I claim 1. Apparatus for burning or roasting solids containing vaporizable combustible material comprising a tiered multiple hearth furnace, said furnace being divided into an upper section and a lower section, means for limiting air available for combustion in said upper section, said sections being separated from each other so that the gases from the lower section do not come in contact with material in the upper section, means for supplyin the solids to the upper section, means for ta ing ofi' vapors from said upper section, means for conveying the solids from said upper section to said lower section, means for taking off gases from said lower section, means for admitting air for combustion to said lower section, and means for discharging the burned or roasted solids from said lower section.

2. Apparatus for burning or roasting solids containin vaporizable combustible material comprising a tiered multiple hearth furnace, said furnace being divided into an upper section and a lower section, means for limiting air available for combustion in said upper section, said sections being separated from each other so that the gases from the lower section do not come in contact with material in the upper section, means for supplyin the solids to the upper section, means for ta ing ofl vapors from said. upper section, means for conveying the solids from said upper section to said lower section, means for taking off gases from said lower section,

means for admitting air for combustion to said lower section, means for admitting vapors taken off from said upper section as fuel for combustion to said lower section, and means for discharging the burned or roasted solids from said lower section.

3. Apparatus for burning or roasting solids containin vaporizable combustible material comprising a tiered multiple hearth furnace, said furnace being divided into an upper section and a lower section, means for limiting air available for combustion in said upper section, said sections being separated from each other so that the gases from the lower section do not come in contact with material in the upper section, means for supplying the solids to the upper section, means for taking off vapors from said upper section, means for conveying the solids from said u per section to said lower section, means or taking off gases from said lower section, means for admitting air for combustion to said lower section, means for admitting vapors taken off from said upper section as fuel for combustion to said lower section at a plurality of levels, and means for discharging the burned or roasted solids from said lower section.

4. Apparatus for burning or roasting solids containing vaporizable combustible material comprising a tiered multiple hearth furnace, said furnace being divided into an upper section in which air available for combustion is limited, an intermediate section and a lower section, the upper section being separated from the intermediate and lower sections so that gases from said intermediate and lower sections do not come in contact with the material in the upper section, means for supplying the solids to the upper section, means for taking 011 vapors from said u per section, means for conveying the solids rom said upper section to the lower section, means for taking off gases from said lower section and passing them into the intermediate section where separation of fines from said gases takes place, means for admitting air for combustion to said lower section and means for discharging the burned or roasted solids from said lower section.

In testimony whereof I afiix my signature.

GEORGE R. LEWERS. 

